If there's any profit to be made from a market trend, that trend is more likely to be volatility than a downturn, as far as I can surmise. They make commission from trades that are made, and at scale that's a lot of profit. It's the same thing that keeps Coinbase profitable in that bear market. Of course I could be wrong, but generally you sometimes hear about the big shorting positions from big players. I don't recall Vanguard traders making the news, and I'm not sure they're involved in options, either.